I guess this is both a warning and a question. I serve local content stored on external drives from my mac running Mojave to my chromebox. I have been running betas and now the golden master of macos Catalina on a separate volume. As of now it does not appear that libreelec can access local storage via zeroconf (nfs) when I am running Catalina. So this is a warning -- if you are using a mac to serve local content, hold off on upgrading system software. As a question -- has anyone found the proper syntax to make this work? I realize that this is an Apple problem.
It turns out that under Catalina external drives are protected by SIP or "System Integrity Protection." You can disable SIP if you care to and all your content will be available.
There is a theory that a zeroconf/NFS client may access files stored on these drives by asking permission and providing credentials, but I guess Kodi would have to actualize that.